Selector system



W. W. HANSEN SELECTOR SYSTEM May 11, 1948.

Filed July 31, 1945 2 Sheets-Sheet 1.

FIG!

M a i mwzm'ozz WILBUR w HANSEN ATTORNEY FIG. 2

H, 1948. w; w. HANSEN 2,441,145

SELECTOR SYSTEM Filed July 31, 1943 2 Sheets-Sheet 2 2 i as on A.EELECTRONIC mAcN:T|c SELEGTOR LOAD Amman AMPLIFIER RELAY RELAY DEVICE 14a \a 2o 22 24 2e FIG. 3

INVENTOR WILBUR W. HANSEN ATTORNEY Patented May 11, 1948 NHTED STATESPATENT OFFICE (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) 16 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates to selector systems, and more particularly tosuch systems discriminatorily responsive to grouped combinations ofpulses for control of remote mechanisms.

In systems of this character, particularly when the remote control is bymeans of radio energy, it is important to guard against intentionalinterference by others, and accidental interference, whether man-made ornatural. It is obviously important to guard against error when theselector is used to detonate a remote explosive device, say a land mine,or to arm the fuse of an explosive device which is later detonated bylocal contact.

The primary object of my invention is to generally improve code selectorsystems.

Another object is to incorporate the above mentioned safeguards.

A further object of the present invention is to provide a selectorsystem controlled by the transmission of a special code combination ofpulses, and in such system to uard against response to the transmissionof the correct code numbers mixed with other incorrect numbers, or thetransmission of the correct code numbers but with long delay betweensome of the successive numbers, or the transmission of man-made ornatural pulses of static which might simulate one or more numbers of thecode.

In accordance with one feature and object of my invention, the receiptof any incorrect number wipes out the effect of all previously receivednumbers, including even correct ones. Moreover, any appreciable delaybetween the transmission of any two numbers of the code combination willwipe out the effect of all previously received numbers. The system maybe so arranged that the entire code-combination of correct numbers mustbe received in proper sequence within a very short time, say tenseconds, or the selector will not respond.

The complete apparatus preferably includes selective radio and audioreceiving circuits, thereby providing first and second stages ofselectivity prior to the action of the selector, the latter providing athird stage of selectivity. However, the complete apparatus is notclaimed in the present application, which instead is directed moreparticularly to the third stage selector. The complete apparatus,including the first and second stages, is more fully disclosed andclaimed in a 2 copending application, Serial No. 599,299, filed June 13,1945, for Selector circuit.

To accomplish the foregoing general objects, and other more specificobjects which will hereinafter appear, my invention resides in theselector elements and their relation one to the other as hereinafter aremore particularly described in the specification, and sought to bedefined in the claims. The specification is accompanied by drawings inwhich Figure 1 shows one particular selector mechansim embodyingfeatures of my invention;

Figure 2 shows the opposite side of the same:

Figure 3 is a block diagram explanatory of the complete apparatus;

Figure 4 is a schematic wiring diagram of a selector embodying featuresof my invention;

Figure 5 illustrates a modification of a detail;

Figure 6 shows the pawl, ratchet, and supply switch mechanism;

Figure 7 is a, transverse section through the banks of contacts of theselector, taken approximately in the plane of the line 1-1 in Figure 1,

but with the arms separated from the contacts for clarity;

Figures 8, 9 and 10 show successive positions in the operation of thebridging and reset relay; and

Figure 11 shows a detail of the bridge opening switch.

The selector as specifically disclosed herein forms a part of aradio-actuated system intended for the remote control of a militaryweapon, typically, a, land mine. The arrangement for this purpose isdiagrammatically illustrated by the box diagram of Figure 3.

Referring to that figure, radio-frequency energy collected on an antennai2 is fed to a preferably highly selective radio-frequency amplifier andbufier stage M, which helps prevent reradiation from a preferablysuperregenerative detector stage It. The latter may be shielded andoperated at low power level to prevent reradiation which would revealthe presence of the land mine to an enemy. The authorized transmissionmay consist of a carrier of predetermined frequency modulated atpredetermined audio frequency, in which case the detector stage IB ispreferably followed by a so-called peaked or selective audio-frequencystage IB. Any enemy transmission would have to employ the correctcombination of radio and audio frequencies to prove effective. Thesecircuits are set forth in greater detail in a copending application,Serial No. 599,299, previously referred to.

The output from the audio-frequency amplifier I 8 may be used to operatean electronic relay 20, controlling a sensitive magnetic relay 22, whichin turn operates a stepping magnet in a selector 24. If the propermultiple-digit code requirement is met at theselector 24, an output isobtained which may be used to actuate whatever load device 26 is soughtto be remotely controlled.

The wiring of the selector is shown in Figure 4. The selector comprisesa plurality of banks of contacts generally designated B, arms generallydesignated A for slidably engaging said banks, and a stepping magnet Swhich actuates a pawland-ratchet mechanism for moving the arms A alongcontact banks B. The selector system further comprises one or morestorage capacitors (C1 and C2) and a current source E for charging thesame. The source E and the capacitors are so connected to the contactsthat one or the capacitors is charged if the arms A are stepped to andbridge predetermined contacts corresponding to' a first digit in thecode number. A charge from the first capacitor C1 is subsequentlytransferred to the second capacitor C: it the arms A are next stepped toand bridge other predetermined contacts corresponding to a second digitin the code. Output terminals T are so connected to certain of thecontacts that a charge from the second capacitor C2 is transferred tothe output terminals if the arms A are stepped to and bridgepredetermined contacts corresponding to a third digit.

be called the dwell contacts. The bridging contacts are open as the armsare stepped toward the dwell contacts, and are closed when the armsreach and dwell on the dwell contacts.

It will be evident that ii' the arms are stepped to contacts number 2,the bridging circuit 54, ll

It will be understood that for a simpler code 7 In the specific selectorhere illustrated, there .are'three banks of contacts generaly designated32, 34, and 36. These may form part of a standard step-by-step relaysuch as is commonly employed in dial telephone switching. One of thesebanks, in this case the bank'ilz, has all of its contacts but oneconnected together and to the storage capacitor C2. The unique contact,in this case the number 2 contact, is connected by means of wires 38'and 40 to a normally closed supply switch 42 and potential source E. Allof the contacts but one of contact bank 36 are connected together and tothe storage capacitor C1. The unique contact, in this case the number 8contact, is connected by means of wire 44 to the output terminal T. Thethird bank, in this case the bank 34, has all of its contacts but threeconnected together and to ground as indicated at 46, the three opencontacts, in this case contacts numbers 2, 5, and 8, corresponding tothe predetermined code combination. Two of the open contacts correspondto the unique contacts of banks 32 and 36. The code number 258 isarbitrary, and has been selected solely for illustration.

There are three arms, 48, 58 and 52, which respectively slidably engagethe contact banks 32, 34, and 36. These arms are connected by means ofleads 54, 56, and 58 to bridging contacts 60, 62, and 64, which whenclosed bridge the arms, and consequently bridge the contacts acrosswhich the arms are disposed when the bridging contacts are closed. Aswill later appear, the bridging contacts are closed by a magnet 66 whenthe arms come to rest or dwell at the end of any series of pulses. Thecontacts on which the arms happen to come to rest may, for convenience,

will connect potential source E through the supply switch 42, conductor40, and conductor 38, to the bottom bank 36, and thence to the firststorage capacitor C1, the circuit being completed by means of conductors66, 58, and 10. 11, however, the arms are stepped to some other number,say i, or 3, etc., the bridging circuit 54, 54, 58 connects the upperand lower banks not only to each other but also to the middle bank 34and thence to ground at 46. It the incorrect number happens to beanother number in the code. say 5 or 8, so that the banks are notgrounded, there is nevertheless'no charging of condenser 01 from sourceE because source E is connected through wires 40 and 38 to only the topcontact number 2, and not to any other contact.

Assuming now that the arms have been stepped properly to contacts number2, and reset, and are then stepped properly to the next number of thecode (in this case, contacts number 5), it will be seen that thebridging circuit 54, 58 will now connect the bottom bank to the top bankand so transfer a charge from condenser C1 upwardly from the bottom bankto the top bank and thence through conductor 12 to the second storagecondenser C2. If, however, the transmitted second number is incorrect,so that the arms dwell on contacts other than number 5, the bridgingcircults 54, 56, 58 connect the top, middle, and bottom banks togetherand to ground. In this way, the charge on capacitor C1 is not only nottrans- Ierred to capacitor C2, but is discharged to ground, thus"wipingout the correct first digit. If the arms happen to dwell on contactsnumber '2, there will be no efiect other than renewed charging ofcapacitor C1, and if the arms happen to dwell on contacts number 8,there will be no effect on terminal T because capacitor C2 has not yetreceived a charge.

Assuming that correct first and second numbers have been transmitted sothat capacitor C2 is charged-and that the arms, after being reset,

are stepped to the correct third number, in this case the number 8, thebridging circuits 54, 5! connect the top bank to contact 8 on the bottombank, thereby connecting capacitor C2 through wire 12 and the bridgingcircuits to'wire and so to the upper terminal T. In this way a chargefrom the storage capacitor C2 is fed to'the output terminals forutilization. If, however, the arms are stepped to some incorrect thirdnumber, the bridging circuit 54, 56, 58 connect the top and bottom banksto the grounded middle bank, and so discharge the capacitors C1 and C2,thereby wiping out the effect of the previously transmitted correctnumbers.

As a further precaution, I provide leak resistors 74 and 16. acrosscapacitors C1 and C2 respectively. These leak resistors may be adjustedto substantially discharge the capacitors in a desired short time, sothat the transmission of the successive code numbers must be completedwell within that time. In the specific case here shown, the leakresistors are selected to discharge the capacitors to 1% the initialcharge in 10 seconds.

The bridging relay acts also as a reset relay. More specifically, magnet56 functions to close not only the bridging contact 60, 62, 54, but alsoreset contacts 18, disposed in series with a reset inwnet 8B. which inturn disengages a holding pawl for the arms. Reset contact I8 closessomewhat later than bridging contacts til, it, ll, thus providing adwell period at the contact to which the arms are stepped.

The mechanism for controlling the bridging and reset relay includes acold cathode thyratron 02, the plate circuit of which is connected tomagnet It by means of wire 84. The opposite end of the magnet isconnected to source E through wires .0 and I and supply switch 42.Assuming the supply switch closed, it will be evident that magnet 66 isenergized whenever thyratron 82 The grid 88 of the thyratron is alsoconnected to source E but through resistors 90 and 82. A firingcapacitor 86 is connected across the grid and cathode of the thyratron,and is itself shunted by shorting contacts 86. The shorting contacts aremechanically actuated by stepping magnet S. thus preventing the buildingup of a charge on the capacitor 84 during stepping of the arms.or,-considered from a difierent viewpoint,

the shorting contacts Sdhold the grid potential of the thyratron down tothe cathode potential, thus preventing firing of the thyratron. However,when the arms reach the last contacts (dwell contacts) to which they arebeing stepped,

the resulting dwell period permits an appreciable charge to build up onthe firing capacitor 94, and the grid 88 of the thyratron goessufliciently positive to fire the thyratron, whereupon magnet 88 is,energized, the bridging contacts and then the reset contacts areclosed, the holding pawl of the arms is released, and the arms are resetby a suitable restoring spring. The resistors 90 and 82 preventappreciable grid current flow when the thyratron fires or, in. otherwords, they reduce the potential from source E to a low enough value atthe grid so that the plate 88 of the thyratron receives the main currentflow through the thyratron. The resistor 9% is selected to form withcapacitor 9d an RC combination having a suitable time constant relativeto the stepping frequency, which is also the closing frequency of theshorting contacts 9t.

In connection with Figure 3, it was mentioned that a relay tube 20controls a sensitive magnetic relay 2?, which in turn controls thestepping magnet of the selector 2%. In Figure 4 the sensitive relay isindicated by a magnet we, controlling an armature I02, which when closedfeeds current through the stepping magnet S. I have equally successfullyemployed a simpler circuit diagrammatically shown in Figure 5, in whichthe sensitive relay magnet 10 A closes contacts "it. thereby energizinga stepping magnet 8th. The capacitor H6 and resistor N2 of Figure 4 areeliminated in the arrangement of Figure 5. because the relay of Figure 5has an antiinduction winding to prevent sparking. when the relay has noanti-induction winding the circuit of Figure 4 is preferable.

A better understanding of the construction and operation of the presentembodiment of my invention will be gained by reference to other figuresof the drawing showing the structural arrange'ment of the relayelements. Referring first to Figure 2, the sensitive relay whichcontrols the stepping magnet is shown at 22, this comprising a normallydeenergized magnet I00 and an armature and movable contact I02,cooperating with a stationary contact it i In the resent circuit theother contact its serves merely as a motionliniiting device.

Referring now to Elem-a1, the stepping magnet or motor magnet isindicated at S and when energized it attractsan armature lit, the end ofwhich carries a pawl 6; for cooperation with a ratchet which is notvisible in Figure 1' because it is concealed by the contact arms A.However, in Figure 6 the contact arms havebeen omitted, thus exposingthe ratchet. I I8. The ratchet works against the pull of a restoring sping 120, and is held in stepped position by a'checkpawl E22; The checkpawl is normally urged inwardly by a leaf spring I24 (Figure 1) bearingagainst a stationary stop pin I26. Pin I28 acts also to limit the returnmovement of the contact arms. This will be clear from Figure 6, in whichthe ratchet has been moved back to initial position 'by'restoring springI20, at which time ;a stop'arm I28 bears against the stop pin-I26. Itwil1.be understood that the teethof the ratchet correspondt thesuccessive contactsin the banks 13 (Figure 1).

The construction of the banks and arms will be clear from Figure '7 inwhich it will be seen that the arms 48, 50, and 52 are each made up of'two thin sheet-metal arms, made of a suitable material such as Phosphorbronze. The two parts of each arm are connected together at their hubends. In Figure 7, the arms are shown separated from thecontact banks,but in assembled position each double arm *straddles one of the banks.The individual contacts are indicated at 32', 3d, and 86'. These areextended at the right-hand end to form the'soldering lugs 32", 34", 3B".The contacts are clamped between arcuate pieces of insulation I 30 andI32. A continuous strip of metal, i, is disposed between insulationstrip I32 and the arms 48, which thus function to connect one of thecontacts 82 to the bottom plate IN. The purpose of this construction ismerely to avoid the need for making a flexible or slip ring connectionto the movable arms, and instead an external connection may readily bemade at the end of the bottom plate I34. The top bank may be completedby means of another strip or insulation i3t. The second and third banksof contacts are constructed in similar fashion, and all three banks areheld tightly together in assembled relationship by means of suitablescrews 4 38. These screws may also function to hold the banks on thechassis plate of the complete selector.

In order not to confuse the drawing the connections between thesoldering lugs of the contacts have been omitted in Figure 1, but itwill be understood that a single-conductor may be used running from onecontact to another but skipping the uniquecontach'this unique contactcorresponding to a code number. In the case of the middle bank, threesuch contacts are skipped, two of them corresponding to the uniquecontacts in the top and bottom-banks, and the third corresponding to themiddle code number. Other connections to the various auxiliary switches,as well as the details of the electron tube sockets, and the capacitorsand resistors associated therewith, have been omitted for the samereason.

The construction of the bridging and reset relay may be described withreference to Figures 2 and 8 through 10. ,The magnet is numbered 66, asin Figure 4. In Figure 2 only the top bridging contact 60 is visible,but in Figures 8, 9, and 10 it will be seen that another bridgingcontact 62 is disposed between the top bridging contact and thestationary contact Ed. The movable contacts are mounted between 'piecesof insulation Mt on an iron armature M2 normally held upward by a tact62 bears against stationary contact 54, doilowing which the springcontact 66 bears against spring contact 62, thus bringing the parts tothe position shown in 'Figure 9, at which time the bridging contacts areclosed, This, it e recoliected on reference to Figure 4, connects threearms A together;

Reverting to Figureij'the armature ricer;

ries a reset contact it) in addition to the brid' contacts justdescribed. In order to show the use 1 layed action of the resetcontacts, they have been drawn above the bridging contacts in Figures 8,

9, and 10, instead of alongside the same. It will be understood,however, that the movable contacts are all mounted on and move with thearmature M2, this being schematically indicated in Figures 8, 9, and bythe dotted lines it. The screw M6 in Figures 2 and 8 is here used merelyas a motion-limiting stop to limit outward movement of the contacts.This screw has accordingly been omitted in Figures 9 and ii Bycomparison of Figures 8, 9, and 10, it will be seen tween increases thedwell time available tocharge the storage condenser C: (Figure 4) Thisis de sirable, though not essential, because there is also some delaydue tothe time required for current to build up in coil 86 and to pullin the check pawl I122.

The restoring action of the arms A is provided by releasing the holdingpawl I22 previously mentioned, and referring to Figure 1 it will be seenthat this is accomplished by energization of the reset magnet 80 whichattracts an armature I48, which may if desired be an extension of thepawl arm. The armature I" also carries a spaced pair of contacts 450,352(see Figure 11) mounted on a piece of insulatiign I54. These normallyengage stationary corit'acts i58, lit, but the contacts are openedwhqthe reset magnet 80 is energized, as will be clear from inspection ofFigure 1.

Referring now to Figure 4, it will be seen that the contacts in questionact as switches in the bridging wires 54 and 58 leading to the bridgingcontacts. These bridge-opening switches destroy the bridging actionduring return movement of the arms A. This prevents grounding of thestorage condensers C1 and C2 through the middle bank of contacts 34 tothe ground 46. Similar precaution is not necessary during the upwardsteppin movement ofthe arms A because at that time the bridging relay isstill open, whereas during the return movement the bridging relay is.

closed.

. In Figure 4 reference was made to a supply switch 42, and referring toFigures 1 and 6 it will be seen that the, switch in question comprisescontacts one of which has a camming portion I" which is eng ed by aninsulation roller-I62 when the arms are in the initial or rest positionshown in Figure 6. However, the moment the arms are stepped to any digitfronrone' through zero, the roller l q2 leavesythe ,ca'mming portion 860and permits tire-contacts to-close.

Reverting to Figure 4, the main purpose of supply switch 42 is to openthe thyratron 82 after it has been fired. During operation ofthelstepping relay the supply switch is closed, so thatfw-hen the seriesof impulses corresponding toany'digit ha'sjbe'en completed,'wlth aresulting dweli lpng enough-.120 charge the firing condenser 94, thethyretronijz fires. This in turn energizes the .maj.'gnet-fifofjthebridging and reset relay with consequent res'etting of the arms toinitial position, at which time the supply switch 42 is opened, thuscutting off the plate and grid supplies to the thyratron, and so openingthe same.

In Figure 4 mention was made of shorting contacts, 96 which shunt thefiring condenser 84 durmg each step of the selector. Referring to Figure1, it will be seen that the shorting switch is made up of a yieldablestationary contact I64 which is engaged by a movable contact I 86mounted on pawl i It and moved by armature H4. Each time the steppingmagnet receives a pulse of. energy, the shorting contact 96 is grounded,thus shorting the firing condenser 94, and preventing it fromaccumulating enough charge to fire the thyratron during normalprogressive stepping of the arms. After each pulse the pawl immediatelyreturns to initial position under influence of a restoring spring 866.When the arms reach the dwell contacts and the pawl is returned, thecontact 96 is open, thus permitting the firing condenser 94 to acquireenough charge to fire the thyratron and so operate the bridging andreset relay.

It is believed that the construction and operation of my improvedselector system will be understood from the foregoing detaileddescription.

Referring to Figure 3, the received signal must first meet theselectivity requirements as to radiofrequency, and audio-frequencymodulation, and if these requirements are met, any pulses or keying ofthe signal are transmitted to the stepping magnet S (Figures 1 and 4) ofthe selector. These step the arms A along the contacts 3 to the dwellcpntacts.= During this stepping operation, the supply switch 42 isclosed and the firing condenser 96 tends to charge but is repeatedlyshorted by the shorting switch 96. At the dwell contacts, however, thefiring condenser accumulates enough charge to fire thyratron 82, whichthen energizes magnet 56 of the bridging and reset relay. This firstcloses the bridging contacts 60," 82, and 64, with results which dependon whether the dwell contact is correct according to the preselectedcode. After closing of the bridging contacts, the reset contacts areclosed. thus energizing the reset magnet "which in turn pulls out theholding pawl and so permits the restoring spring I20 (Fig.- ure 6) topull the arms back to initial position. When the arms reach initialposition, the supply switch is opened, thus opening thyratron 82 and sodeenergizing the bridging and'reset magnet 85. Thereupon another seriesof impulses are received, which again step the arms to dwell contacts.

If the .dwell contacts turn out tobe correct, which in the present caserequires the numbers 2, 5, and 8, the action is as follows: when dwellconwires .40 and 38 through the upper contact to the lower bank andthence to storag capacitor C1, thus charging that capacitor. Duringreturn movement of the contact arms the capacitor is not dischargedbecause bridge-opening switches I50, I 52 are opened. When the arms arenext stepped to contacts number 5, some of the charge on the capacitorC1 is transmitted from the lower bank to the upper bank and thencethrough conductor 12 to the second storage capacitor C2, thus chargingthat capacitor. During the return movement of the arms, the capacitorsare not discharged because the bridge-opening switches I50, I52 areopen. If the arms are next stepped to contacts number 8, some of thecharge of the second storage capacitor C2 is transmitted through wire 12and the upper bank to the lower contact number 8 and thence through wire44 to the upper terminal '1'. The circuit is completed by Wires I10, 66,and 88 to ground or to lower terminal E. The resulting pulse of energymay be utilized for any desired purpose, as for example to fire anotherthyratron or a sensitive relay, which in turn is arranged to detonate anexplosive or to arm a weapon or for any other remote-control purpose.

If any received number differs from a code number, both storagecapacitors are grounded and discharged. If the received numbers are inimpropersequence the condensers will not be charged, or the charge willnot be transferred. Even if the correct numbers are received in correctsequence but only after some delay, the storage capacitors aredischarged by the operation of the leak resistors H, 16. Anyirregularity or delay in transmitting a particular group or series ofpulses for a particular number will permit the firing condenser to firethe thyratron and so restore the arms to initial position.

It is believed that the advantages of my improved selector system willbe apparent irom the foregoing description. It will also be apparentthat while I have shown and described my invention in a preferred form,many changes and modifications may be made in the structure disclosedwithout departing from the spirit of the invention, as sought to bedefined in the following claims.

I claim:

1. A selector system comprising an electrical power source, a storagecondenser, means to con- 'nect the power source to the storage condenserwhen a correct first signal is received but not when any other signal isreceived, means to transfer a charge from the storag condenser when acorrect second signal is received but to ground and discharge thecondenser if any other second signal is received, and a leak resistorconnected across said storage condenser to substantially dis charge thesame in a predetermined short time if the correct first and secondsignals have not been received within that time.

2. A selector system comprising an electrical power source, first andsecond storage condensers. means to connect the power source to thefirst storage condenser when a correct first signal is received but notwhen an other signal is received, means to transfer a charge from thefirst storage condenser to the second storage condenser when a correctsecond signal is received but to ground and discharge the firstcondenser if any other second signal is received, and means to connectthe second storage condenser to output terminals for utilization of thecharge when the correct third signal is received, but to ground anddischarge the first and second condensers if any other third signal isreceived.

3. A selector system comprising an electrical power source, firstandsecond storage condensers, means to connect the power source to thefirst storage condenser when a correct first signal is received, meansto transfer a charge from the first storage condenser to the secondstorage condenser when a correct second signal is received, means toconnect the second storage condenser to output terminals for utilizationof the charge when the correct third signal is received, and means tosubstantially discharge said first and second storage condensers in apredetermined short time if the correct first, second, and third signalshave not been received within that time.

4. A selector system comprising an electrical power source, first andsecond storage condensers, means to onnect the power source to the firststorage co denser hen a correct first signal is received but not whenany other signal is received, means 0 transfer a charge from the firststorage condenser to the second storage condenser when a correct secondsignal is received but to ground and discharge the first condenser ifany other second signal is received, means to connect the second storagecondenser to output terminals for utilization of the charge when thecorrect third signal is received, but to ground and discharge the firstand second condensers if any other third signal is received, and leakresistors connected across said first and second storage condensers tosubstantially discharge the same in a predetermined short time if thecorrect first, second, and third signals have not been received withinthat time.

5. A selector system comprising a plurality of banks of contacts, armsfor slidably engaging said banks, a stepping magnet with pawl andratchet mechanism for moving said arms over successive contacts of saidbanks, a storage capacitor, a current source for charging saidcapacitor, said source and capacitor being so connected to certaincontacts of said banks that the capacitor is charged only if the armsare stepped to and bridge predetermined contacts, and output terminalsso connected to certain of said contacts that a charge from thecapacitor is transferred to the output terminals only if the arms arestepped to and bridge predetermined contacts.

6. A selector system comprising a plurality of banks of contacts, armsfor slidably engaging said banks, a stepping magnet with pawl andratchet mechanism for moving said arms over successive contacts of saidbanks, a storage capacitor, a current source for charging saidcapacitor, said source and capacitor being so connected to certaincontacts of said banks that the capacitor is charged only if the armsare stepped to and bridge predetermined contacts, output terminals soconnected to certain of said contacts that a charge from said capacitoris transferred to the output terminals only if the arms are stepped toand bridge predetermined contacts, and a leak resistor connected acrosssaid capacitor to discharge the same if the charge thereon is notutilized within a predetermined short time.

7. A selector system comprising a plurality of banks of contacts, armsfor slidably engaging said banks, a stepping magnet with pawl andratchet mechanism for moving said arms over successive contacts of saidbanks, a storage capacitor, a current source for charging saidcapacitor, said source and capacitor being so connected to certaincontacts of said banks that the capacitor is charged only if the armsare stepped to and bridge predetermined contacts, and output terminalsso connected to certain of 11 said contacts that a charge from thecapacitor is transferred to the output terminals only if the arms arestepped to and bridge predetermined contacts, connections to dischargethe capacitor when the arms bridge incorrect contacts, and bridgeopening means to open during movement of the arms the bridgingconnection provided by the arms.

8. A selector system comprising a plurality of banks of contacts, armsfor slidably engaging said banks, a stepping magnet with pawl andratchet -mechanism for moving said arms over successive contacts of saidbanks, a first storage capacitor, a current source for charging saidcapacitor, said source and capacitor being so connected to certaincontacts of said banks that the ca'pacitor is charged only if the armsare stepped to and bridge predetermined contacts, a second storagecapacitor so connected to certain of said contacts that a charge fromthe first capacitor is transferred to the second capacitor only if thearms are stepped to and bridge predetermined contacts, and outputterminals so connected to certain of said contacts that a charge fromthe second capacitor is transferred to the output terminals only if thearms are stepped to and bridge predetermined contacts.

9. A selector system comprising a plurality of banks of contacts, armsfor slidably engaging said banks, a stepping magnet with pawl andratchet mechanism for moving said arms over successive contacts of saidbanks,a first storage capacitor, a current source for charging saidcapacitor, said source and capacitor being so connected to certaincontacts of said banks that the capacitor is charged only if the armsare stepped to and bridge predetermined contacts, a second storagecapacitor so connected to certain of said contacts that a charge fromthe first capacitor is transferred to the second capacitor only if thearms are stepped to and bridge predetermined contacts, output terminalsso connected to certain of said contacts that a charge from the secondcapacitor is transferred to the output terminals only if the arms arestepped to and bridge predetermined contacts, ground connections toground and discharge the capacitors when the arms bridge incorrectcontacts, and bridge opening means to open during movement of the armsthe bridging connection provided by the arms.

10. A selector system comprising a, plurality of banks of contacts, armsfor slidably engaging said banks, a stepping magnet with pawl andratchet mechanism for moving said arms over successive contacts of saidbanks, a first storage capacitor, a current source for'charging saidcapacitor, said source and capacitor being so connected to certaincontacts of said banks that the capacitor is charged only if the armsare stepped to and bridge predetermined contacts, a second storagecapacitor so connected to certain of said contacts that a. charg fromthe first capacitor is transferred to the second capacitor only if thearms are stepped to and bridge predetermined contacts,

output terminals so connected to certain of said contacts that a chargefrom the second capacitor is transferred to the output terminals only ifthe arms are stepped to and bridge predetermined contacts, and a leakresistor connected across each of said capacitors to discharge the sameif the charge thereon is not transferred within a predetermined shorttime. p

11. A selector system comprising three banks of contacts, one bankhaving all of the contacts but one connected together and to a storagecapacitor, the unique contact being connected to a current supplysource, another bank having all of the contacts but one connectedtogether and to another storage capacitor, the unique contact beingconnected to an output terminal, the third bank having all of itscontacts but three connected together and to ground, the three opencontacts corresponding to a predetermined code combination, and two ofthem corresponding to the aforesaid unique contacts, arms slidablyengaging said banks of contacts, a stepping magnet with pawl and ratchetmechanism for moving said arms over said contacts, the arrangement beingsuch that when the arms are stepped to the first contacts of thepredetermined code one of the storage condensers is charged by thesupply source, when the arms are stepped to the second contacts of thepredetermined code a charge is transferred from the first storagecondenser to the second storage condenser, and when the arms are steppedto the third contacts of the code a charge is transferred from thesecond storage condenser to the output terminal for utilization, butwhen the arms are stepped to any incorrect contact the storagecondensers are discharged.

12. A selector system comprising three banks of contacts, one bankhaving all of the contacts but one connected together and to a storagecapacitor, the unique contact being connected to a current supplysource, another bank having all of the contacts but one connectedtogether and to another storage capacitor, the unique contact beingconnected to an output terminal, the third bank having all of itscontacts but three connected together and to ground, the three opencontacts corresponding to a predetermined code combination, and two ofthem corresponding to the aforesaid unique contacts, arms slidablyengaging said banks of contacts, a stepping magnet with pawl and ratchetmechanism for moving said arms over said contacts, the arrangement beingsuch that when the arms are stepped to the first contacts of thepredetermined code one of the storage condensers is charged by thesupply source, when the arms are stepped to the second contacts of thepredetermined code a charge is transferred from the first storagecondenser to the second storage condenser, and when the arms are steppedto the third contacts of the code a charge is transferred from thesecond storage condenser to the output terminal for utilization, butwhen the arms are stepped to any incorrect contacts the storagecondensers are discharged, said storage condensers further having leakresistors connected thereacross to discharge the same if the proper codecombination is not received within a predetermined short time.

13. A selector system comprising three banks of contacts, one bankhaving all of the contacts but one connected together and to a storagecapacitor, the unique contact being connected to a current supplysource, another bank having all of the contacts but one connectedtogether and to another storage capacitor, the unique contact beingconnected to an output terminal, the third bank having all of itscontacts but three connected together and to ground, the three opencontacts corresponding to a predetermined code combination, and two ofthem corresponding to the aforesaid unique contacts, arms slidablyengaging said banks of contacts, a stepping magnet with pawl and ratchetmechanism for moving said arms over said contacts, the arrangement beingsuch that when the arms are stepped to the first contacts of thepredetermined code one of the storage condensers is charged by thesupply source, when the arms are stepped to the second contacts of thepredetermined code a charge is transferred from the first storagecondenser to the second storage condenser, when the arms are stepped tothe third contacts of the code a charge is transferred from the secondstorage condenser to the output terminal for utilization, but when thearms are stepped to any incorrect contacts the storage condensers aredischarged, a bridging relay for connecting the arms together when theydwell at the contact to which they have been stepped, a reset means forrestoring the arms to original position, and a bridge opening switch toopen the connection between the arms during their return movement.

14. A selector system comprising three banks of contacts, one bankhaving all of the contacts but one connected together and to a storagecapacitor, the unique contact being connected to a current supplysource, another bank having all of the contacts but one connectedtogether and to another storage capacitor, the unique contact beingconnected to an output terminal, the third bank having all of itscontacts but three connected together and to ground, the three opencontacts corresponding to a predetermined code combination, and two ofthem correspondingto the aforesaid unique contacts, arms slidablyengaging said banks of contacts, a stepping magnet with pawl and ratchetmechanism for moving said arms over said contacts, the arrangement beingsuch that when the arms are stepped to and bridge the first set ofcontacts of the predetermined code one of the storage condensers ischarged by the supply source, when the arms are stepped to and bridgethe second set 01 contacts of the predetermined code a charge istransferred from the first storage condenser to the second storagecondenser, and when the arms are stepped to and bridge the third set ofcontacts of the code a charge is transferred from the second storagecondenser to the output terminal for utiliza but when the arms arestepped to and bridge any incorrect contacts at any time the storagecondensers are discharged, said storage condensers further having leakresistors connected thereacross to discharge the same it the proper codecombination is not received within a predetermined short time," abridging relay for connecting the arms when they dwell at the contact towhich they have been stepped, a reset means for restoring the arms-tooriginal position, and a bridge opening switch to open the connectiontion,

between the arms during their return movement.

15. A selector system comprising a multi-position switch, a steppingmagnet for moving said switch from .a normal position, a reset means forrestoring said switch to said normal position, said reset meanscomprising a grid-controlled electron tube, a firing circuit including acharging capacitor connected across the cathode to grid circuit of saidtube, a contact operated by said stepping magnet to intermittently shortcircuit said capacitor upon each operation of said stepping magnet. andmeans in the plate circuit of the tube to operate said reset means whensaid tube is fired.

16. A selector system comprising a multi-position switch for selecting acircuit, a stepping I magnet for moving said switch from a normalposition, a reset magnet for restoring said switch to said normalposition, a relay including an operating coil and a plurality ofcontacts, and means for controlling the operation oi. said relay, saidlast-named means comprising a grid-controlled electron tube, a potentialsupply source connected to the grid of said tube, a firing circuitincluding a charging capacitor connected across the oathode to gridcircuit of 'said tube, means to momentarily short said capacitor eachtime said stepping magnet operates, a potential supply source connectedto the plate of said tube through said operating coil, at least one ofsaid contacts cooperating with said switch to control the circuitselected by said switch when said tube fires and energizes saidoperating coil, another ofsaid contacts being a delayed-action contactand operating to energize said reset-magnet after the closing of saidone of said contacts.

. I WIBBUB, W. HANSEN.

REFERENCES CITED The following references are of record inthe 40 file ofthis patenti UNITED STATES PATENTS

